Bavaria's Interior Minister Joachim Herrmann said police received intelligence the group was planning a massacre with five to seven suicide bombers as revellers welcomed in the New Year.

The information prompted Munich Police to warn the public to avoid crowds in the German city, just an hour before midnight struck.

Image:Authorities received 'very concrete information' about the threat

Two major train stations were evacuated and services at both terminals were suspended on New Year's eve.

As a result, there were severe delays on the rest of the public transport network as partygoers tried to get home.

In the early hours of the morning, Munich Police confirmed the stations have since been reopened.

"Munich Central Station and the railway station Pasing are meanwhile open again," police said on their official Twitter account.

Image:Munich's key rail stations are empty, and trains are not currently stopping

"We will remain on site and keep our eyes open."

Mr Herrmann told a news conference that authorities had received "very concrete information" about the attack.

It has been reported that French intelligence agencies had notified Munich officials about the terror threat.

Torben Ostermann, a German journalist in Munich, told Sky News: "It's just now 2016 and people are celebrating the New Year like nobody seems to know about the terrorist warning.

Image:Police closed two major rail stations in the German city

"There is nobody in the main station at the moment, but the atmosphere in Munich is like a normal New Year. It's a bit weird though that we have a terrorist warning and people are firing off their fireworks."

This is the second time that Munich's central station has been shut down over a terrorism threat in recent months, he added.

Despite security officials being on heightened alert in Germany, a firework display in Berlin went ahead as planned.

Security fears in Europe were heightened by Belgium's decision to cancel New Year's Eve celebrations in Brussels, citing a suspected plot to carry out an attack in the capital.

Belgian police said late on Thursday that three people had been arrested for questioning as part of an investigation into the plot.